Particle suspensions of flocculating polymer powders and powder flocculant polymer blends

ABSTRACT

Powder blends are described comprising blends of particulate water soluble high molecular weight polymer flocculants. The polymer flocculants can include polyethylene oxide, polyacrylamide, copolymers thereof and combinations thereof. The powder blends allows the use of fine powders while reducing potential air quality and safety issues. The powder blends can be used for waste water purification, fiber dewatering, and the like. The powder blends can be diluted by a water dilution flow prior to entering a waste water stream.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/092,385, filed Nov. 27, 2013, which is hereby incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The invention relates to suspensions of polymer particles in anon-dissolving liquid, in which the polymers are generally suitable asflocculants for waste water treatment. The invention further relates todesirable powder flocculant particle blends. The invention furtherrelates to use of flocculent particle suspensions and/or powder blendsfor the treatment of waste water, fiber dewatering and other uses.

BACKGROUND OF THE INVENTION

Various waste streams have particulate contaminants that should beremoved or concentrated for proper disposal. Traditionally, ponds havebeen used for dewatering the sludge or slime, but ponding is undesirabledue to large areas of lands needed as well as associated environmental,economic, aesthetic and safety reasons. Addition of flocculants to thewaste stream can facilitate concentration of particulate wastes. Inparticular, phosphate mining produces clay and clay like particulates.Economic constraints drive the use of flocculants with respect toefficiency and cost of the processing. Flocculants can also beeffectively used in paper mill operations with respect to treatment ofwastewater as well as a sheet formation aid or other application fordewatering fibers.

SUMMARY OF THE INVENTION

In the first aspect the invention pertains to a powder blend comprisinga particulate polyethylene oxide having an average molecular weight ofat least about 100,000 g/mol and a particulate polyDadmac. Generally thepowder has a concentration of polyethylene oxide from about 1 weightpercent to about 60 weight percent.

In further aspects the invention pertains to a method for treating aliquid, the method comprising delivering a powder blend of flocculatingpolymers from a reservoir into an aqueous treatment stream at a selectedconcentration, the delivering process comprising direct delivery ofpowder blend into the aqueous waste flow and/or delivering the powderblend into a dilution water flow to form an initial aqueous combinationthat is flowed into the treatment stream within 5 minutes of forming thecombination. Generally, the powder blend comprises a particulate watersoluble flocculant polymer different from polyDadmac having a molecularweight of more than 100,000 g/mol and polyDadmac. Additionally, ingeneral, the powder blend has a concentration of flocculant polymer fromabout 1 weight percent to about 60 weight percent, and the flocculantpolymer has a particulate size providing for dissolving into water atlow concentration in no more than about 5 minutes.

In other aspects, the invention pertains to a method for treating aliquid, the method comprising the step of delivering a suspensioncomprising a flocculating polymer from a reservoir into an aqueous wastestream at a selected concentration. In some embodiments, the deliveringprocess can comprise delivery of the polymer suspension into a dilutionwater flow to form an initial aqueous combination that is flowed intothe process stream within 5 minutes of forming the combination. Thepolymer suspension can comprise particulate polyethylene oxide suspendedin a liquid polyether polyol having a molecular weight of at least about150 g/mol.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top schematic view of the layout of a waste treatmentfacility involving the delivery of a polymer flocculant into a wastestream from mineral processing stations as the tailings, i.e., the wastestream, flow to a thickening tank (thickener).

FIG. 2 is fragmentary schematic view of the suspension delivery systemconfigured to direct flocculant polymers into the waste stream using awater dilution flow.

FIG. 3 is a fragmentary schematic view of the dry powder delivery systemconfigured to direct flocculant polymers into the waste stream using awater dilution flow.

FIG. 4 is a side view of 7 samples of flocculant polymers in asuspension following settling.

DETAILED DESCRIPTION

A convenient format has been developed for the delivery of smallparticles of a flocculating polymer or polymer blends as a suspension inmoderate molecular weight polyethylene glycol and/or polypropyleneglycol liquid. The suspension generally has a relatively high quantityof polymer particulates for efficient delivery of the polymer particles.Desirable polymer blends can also be delivered in powder form to takeadvantage of desirable flocculant properties of the polymer blends.Flocculating polymers, such as polyethylene oxide, polyacrylamide,polyDadmac, Dadmac-acrylamide copolymers and combinations thereof, aregenerally high molecular weight water soluble polymers that can beeffectively used for water quality treatment, fiber dewatering and thelike. The polymer particles generally are water soluble and essentiallyinsoluble in the liquid of the suspension, so that relatively highconcentrations of the polymer can be suspended without gelling, whichcan increase the viscosity to undesirable levels. Handling and shippingof fine powders can be problematic for many reasons including, amongothers, potential air quality and safety issues. These handling andsafety issues can be particularly problematic at points of deliverywhere flocculant chemicals are delivered from suitable storagecontainers, generally without access to sophisticated handling equipmentand highly skilled technicians. The suspensions described herein can beadapted to simplify storage at production facilities, transportationusing liquid handling containers and convenient delivery with reducedair quality issues. Similarly, the powder blends can be advantageouslyused to achieve desired effectiveness from the flocculants withconvenient handling and suitable delivery systems adaptable for thematerials. In some embodiments, the suspensions and/or powder polymerblends can be mixed at point of delivery and metered into a waste waterflow that then proceeds to a settling tank or the like where theflocculating polymers settle for separation from the water. Similarly, asuspension and/or polymer blend can be used to deliver flocculatingpolymers for fiber dewatering both for waste water treatment and paperformation.

Polymers generally used as flocculants are water soluble high molecularweight compositions. Flocculant polymers can be useful for the treatmentof various water flows such as involve in coal mining, mineral miningoperation, fiber dewatering, paper processing or paper sheet formationoperations. Such processing with flocculant polymers can be useful toprovide or facilitate water clarification, suspended solids separation,treatment flow thickening, dissolved air floatation, selective mineralseparation, dredging, belt press or centrifuge dewatering, settling pondor reservoir impoundment, paper sheet formation, stickies control, paperdrainage aid, and/or fiber dewatering. While the polymers are generallywater soluble, the flocculants tend to agglomerate and form colloids atappropriate concentrations in water, which may be driven at least inpart by the presence of particulate or fibrous contaminants in thewastewater. Due to colloid formation and agglomeration, the flocculantswith trapped impurities can settle from the flow. As described furtherbelow, settling tanks can be used to separate flocculants with trappedimpurities from the liquid so that purified water can be separated fromagglomerated flocculants/waste, which can be separately removed forfurther processing. Polymer blends can introduce particular efficacy ofeach polymer that has been found to provide for improved effectivenessoverall based on total polymer use. As described herein, in someembodiments, the polymers can be selected so that simultaneous additionto a waste stream can be particularly effective to take advantage of theproperties of the respective polymers.

Polyethylene oxide is typically supplied as a fine free flowing powderused for the manufacture of a number of different pharmaceutical andpersonal care applications. Commercially, there are a few various gradesof polyethylene oxide particle sizes available to end users. Inmanufacture, some polyethylene oxide powders are screened to remove theunwanted, extremely fine polyethylene oxide powder (fines). In the enduse application, the extremely fine properties of the screened finesmake handling difficult. The dust further limits the by-products' enduses. The suspensions described herein provide a convenient and safeapproach for the effective use of ultrafine polymer particles. Based onthe discovery of the convenient approach for the delivery of PEOpowders, this approach has been found to be similarly convenient for thedelivery of other high molecular weight flocculating polymers.

In corresponding embodiments, the suspensions comprise solid and liquidcomponents. In particular, with respect to solid components, thesuspensions generally can comprise from about 5 weight percent to about60 weight percent flocculant polymer particles, in further embodimentsfrom about 10 weight percent to about 55 weight percent, and inadditional embodiments from about 12 weight percent to about 50 weightpercent flocculant polymer particles. The liquid of the suspensiongenerally comprises a liquid polyether polyol, e.g., diol or triol, withoxyethylene repeat units along the polymer backbone, which generallyhave moderate molecular weights, such as polyethylene glycol (PEG,HO—(CH₂—CH₂—O—)_(n)H), propylene glycol (PPG, HO—(CH₂—CHCH₃—O—)_(n)H),copolymers thereof or a mixture thereof (PEG/PPG) as the primarycomponent or only component. PEG and PPG are ethers with two terminalhydroxyl groups and can be moderately viscous compositions, whichinfluences the viscosity of the suspension. Glyceryl ether polymers arecommercial polymers with PEG or PPG reacted with a glycerine molecule toform an ether linkage with the resulting molecule having three terminalhydroxyl groups. (Dow®, PT-series of polymers). Specifically, the liquidof the suspension can comprise at least about 75 weight percent, infurther embodiments at least about 80 weight percent and in additionalembodiments at least about 90 weight percent PEG/PPG. Polymers generallyhave a distribution of molecular weights, and the PEG generally has anaverage molecular weight from about 200 g/mole to about 700 g/mole andin further embodiments from about 300 g/mole to about 650 g/mole. PEG400 (average molecular weight 380-420), PEG 600 (average molecularweight 580-620) and mixtures thereof can be effectively used.Polypropylene glycols can have suitable viscosities at average molecularweights in the several thousands, and are commercially available, forexample, from Dow Chemical. Glyceryl ether polymers with three terminalhydroxyl groups are similarly commercially available with similarviscosities and other properties. Also, copolymers ethylene oxide andpropylene oxide are commercially available. The liquid can be selectedto not significantly dissolve the polymer particles. While thesuspensions can consist essentially of flocculant polymer particles andliquid polyether glycol, e.g., PEG/PPG, other minor components can beincluded in the suspension if desired to modify the properties of thesuspension, such as coloring agents, viscosity modifiers, surfactants,or the like, generally in amounts of no more than about 5 weight percenteach.

Polyethylene glycol (PEG), polyethylene oxide (PEO), orpoly(oxyethylene) (POE) refers to an oligomer or polymer of ethyleneoxide. The three names are chemically synonymous, but historically PEGhas tended to refer to oligomers and polymers with a molecular massbelow 20,000 g/mol, PEO to polymers with a molecular mass above 20,000g/mol, and POE to a polymer of any molecular mass. PEG compositions canbe liquids or low melting solids, depending on the molecular weights ofthe polymer. PEG 400 generally refers to a PEG formulation with anaverage molecular weight between 380 g/mole and 420 g/mole. PEG 400 iscommercially available, for example, as Dow CARBOWAX™ PEG 400. PEG 600generally refers to a PEG formulation with an average molecular weightbetween 570 g/mole and 630 g/mole. Above a molecular weight of roughly800 g/mole, PEG can be a waxy paste like material at room temperature.

Polyethylene oxide can be represented by the formulaH—(O—CH₂—CH₂)_(n)—OH, where n refers to the degree of polymerization,and for high molecular weight polymers, n is large. Low molecular weightvariations of this polymer can be called polyethylene glycol or PEG. Thenature of the polymer can be characterized by the average molecularweight and suitable polymers can be linear or branched. In someembodiments, the average molecular weight of the polyethylene oxide canbe at least about 100,000 g/mol, in further embodiments at least about 1million g/mol, in other embodiments from about 3 million g/mol to about15 million g/mol, and in additional embodiments from about 4 milliong/mol to 11 million g/mol. A person of ordinary skill in the art willrecognize that additional ranges of polyethylene oxide (PEO) molecularweight within the explicit ranges above are contemplated and are withinthe present disclosure. Suitable commercial high molecular weightpolyethyelene oxides are available from Dow Chemical, for example,Polyox WSR™ 308 or UCARFLOC™ 309, 304, etc. Particles of high molecularweight PEO in commercial distribution generally have an average particlediameter of roughly 150 microns, and the particle may be sieved toreduce the presence of small particles, such as particles with adiameter less than about 75 microns. These commercial PEO materials canbe conveniently distributed in the suspensions described herein. Basedon the suspensions described herein, polymer particles with a smallaverage particle diameter as well as mixtures of particles with variousparticle sizes can be conveniently handled. In some embodiments, the PEOparticles (PEO fines) can comprise at least about 10 weight percentparticles with a particle diameter of no more than about 75 microns, infurther embodiments at least about 60 weight percent with a particlediameter of no more than about 75 microns, in additional embodiments atleast about 80 weight percent with a particle diameter of no more thanabout 75 microns, and in other embodiments at least about 10 weightpercent with a particle diameter no more than about 50 microns. A personof ordinary skill in the art will recognize that other particle sizedistributions within the explicit ranges above are contemplated and arewithin the present disclosure.

Polyacrylamide is represented by the formula —(CH₂CH(CONH₂))_(n)—, whichis an amide form of polyacrylic acid. Copolymers of acrylamide can besimilarly referred to as an acrylamide, and various copolymers introducean ionic character into the polymer. For example, some polyacrylamidesare copolymers of acrylamide and acrylic acid. Thus, a polyacrylamidecan be non-ionic, anionic, cationic or amphoteric, and generally thesevarious forms of polyacrylamide are suitable for forming thesynergistically improved flocculant compositions. Chargedpolyacrylamides can be designed with varying amounts of copolymersconstituents to vary the amount of charge, e.g., with charged monomersgenerally varying from about 10 to about 50 percent of the polymerchain. The lab bench results below suggest that the charge is not asignificant parameter for the flocculant function of the polyacrylamidesin the polymer blends. In general, anionic polyacrylamides have founduse in the waste stream treatment process. The molecular weight of thepolyacrylamide has been found to be a significant aspect with respect tothe discovered improvement of the polymer blends. In particular, it isgenerally desirable for the polyacrylamide to have a higher averagemolecular weight relative to the average molecular weight of thepolyethylene oxide. Generally, the polyacrylamide has an averagemolecular weight of at least about 16 million g/mol, in furtherembodiments at least about 18 million g/mol, and in further embodimentsat least about 19 million g/mol, and particularly improved results havebeen discovered for polyacrylamides with an average molecular weight ofat least 22 million g/mol, in further embodiments at least about 22.5g/mol, in some embodiments at least about 23 million g/mol, inadditional embodiments at least about 24 million g/mol and in otherembodiments at least about 25 g/mol. A person of ordinary skill in theart will recognize that additional ranges of molecular weights withinthe explicit ranges above are contemplated and are within the presentdisclosure. Suitable high molecular weight polyacrylamides are availablecommercially, for example, from Kemira™ (e.g., 130A 18-20M mw), SNFFloeger™ (e.g., 934VHM 20-22M mw) and Hengju Polymers (Hengflox™).

Recently it has been discovered that synergistic flocculant propertiescan be obtained from a blend of very high molecular weight PEO andpolyacrylamides. For the desirable blends, in general, the polyethyleneoxide has an average molecular weight of at least 1 million grams/mole(g/mol), and the polyacrylamide generally has an average molecularweight of at least about 22.5 million g/mol. Generally, the polymerblend has a weight ratio of polyethylene oxide to polyacrylamide fromabout 0.667 to about 5, in further embodiments from about 0.75 to about4.5, in additional embodiments from about 0.85 to about 4.25, and inother embodiments from about 1 to about 4. Also, the polymer blend cancomprise at least about 35 weight percent polyethylene oxide, in furtherembodiments from about 45 weight percent to about 90 weight percent, andin additional embodiments from about 50 weight percent to about 85weight percent polyethylene oxide. A person of ordinary skill in the artwill recognize that additional ranges within the explicit compositionranges above are contemplated and are within the present disclosure.These blends can be directly formed into the suspensions describedherein for convenient shipping and delivery for use of the polymerblends. These blends of PEO and polyacrylamides are described further incopending U.S. patent application Ser. No. 13/861,901 to Holt, entitled“Polymer Blends for Flocculation,” incorporated herein by reference.

PolyDadmac or polydiallyldimethylammonium chloride ((C₈H₁₆NCl)_(n)) is acationic homopolymer that can be useful as a flocculant agent.Copolymers of Dadmac and acrylamides as well as other copolymers ofDadmac are similarly available commercially and are similarly suitableflocculant applications as an anionic, cationic or neutral copolymer.PolyDadmac and copolymers thereof generally can have an averagemolecular weight of at least about 100,000 g/mole, in furtherembodiments at least about 1,000,000 g/mole and can be desirable ataverage molecular weights of about 5,000,000 to 30,000,000 g/mole.PolyDadmac can be effectively provided in small particulate form, e.g.,microbeads, or in larger particulate sizes, such as granules. Forflocculant use, polyDadmac particles generally have an average particlediameter from about 0.5 microns to about 150 microns. A person ofordinary skill in the art will recognize that additional ranges ofaverage particle diameter within the explicit ranges above arecontemplated and are within the present disclosure. PolyDadmac generallycan be dissolved in water at high concentrations as a viscous liquidwithout gel formation, but the suspensions described herein ofpolyDadmac can be desirable for flocculant applications. In particular,in contrast with some other flocculant polymers polyDadmac has beenfound to be more effective as a flocculant when added in particulateform directly into a waste stream without first dissolving in water.While the delivery of liquid polymer solutions is convenient from ahandling perspective, the desirability of delivery of particulatepolyDadmac into a waste water flow is described in European patent0536194B to Payne et al., entitled “Purification of Aqueous Liquor,”incorporated herein by reference. Through the delivery of thesuspensions described herein, the convenience of liquid phase deliverycan be combined with the advantages of the delivery of undissolvedpolyDadmac into the waste water flow.

The suspensions thus provide a mechanism for liquid delivery of theparticulate polyDadmac to provide for desirable handling while obtainingthe good performance provided by the particulate material. In thesuspensions described herein, particles of polyDadmac or(Dadmac-acrylamide)copolymers are similarly suspended in anon-dissolving fluid of polyether polyol, e.g., PEG/PPG. Additionally,blends of PEO and polyDadmac can be desirable with respect to theresulting flocculant properties. Generally, a polymer blend for deliveryas a suspension can have a weight ratio of polyethylene oxide topolyDadmac from about 0.667 to about 5, in further embodiments fromabout 0.75 to about 4.5, in additional embodiments from about 0.85 toabout 4.25, and in other embodiments from about 1 to about 4. Also, thepolymer blend of polyDadmac and PEO for delivery as a suspension cancomprise at least about 35 weight percent polyethylene oxide, in furtherembodiments from about 45 weight percent to about 90 weight percent, andin additional embodiments from about 50 weight percent to about 85weight percent polyethylene oxide. A person of ordinary skill in the artwill recognize that additional ranges within the explicit compositionranges above are contemplated and are within the present disclosure.

Powder blends of polyDadmac and a distinct flocculant polymer, such aspolyethylene oxide (PEO) and/or polyacrylamide, have been similarlyfound to provide for desirable handling while obtaining the goodperformance provided by the individual particulate materials. Inparticular, the powder blends described herein reduce the handlingproblems associated with very fine polyethylene oxide powders andimprove flowability through dry feed equipment. Similarly, the blendsprovide improved flocculant function for a quantity of polymer based onthe desirable effects of using polyDadmac in combination with otherflocculant polymers. In general, the polymer blend of polyDadmac anddistinct flocculant polymer, such as PEO, can comprise at least about 5weight percent polyDadmac, in some embodiments at least about 10 weightpercent polyDadmac, in additional embodiments at least about 35 weightpercent polyDadmac, in further embodiments from about 40 weight percentto about 95 weight percent and in other embodiments from about 45 toabout 85 weight percent PolyDadmac. The remaining weight of the blendsgenerally comprises one or more other particulate flocculant polymers,such as PEO, polyacrylamide or blends there, although a small amount ofadditives, such as a flow agent can be added. With respect to PEO,especially PEO fines, as the distinct flocculant polymer, the powderblend can comprise from about 1 weight percent to about 60 weightpercent polyethylene oxide, in further embodiments from about 5 weightpercent to about 55 weight percent, and in additional embodiments fromabout 10 weight percent to about 50 weight percent polyethylene oxide.The blends can improve handling and reduce dust issues that mayotherwise be encountered with the PEO fines. In some embodiments,powdered polyethylene oxide can be a fine PEO powder with an averageparticle diameter of no more than about 75 microns and in furtherembodiments no more than about 50 microns. As noted above, the PEOparticulates can be described with respect to distributions of particlesizes, and these distributions can be applied also to the powder blends.A person of ordinary skill in the art will recognize that additionalranges within the explicit composition ranges above are contemplated andare within the present disclosure.

The powders blends can be assembled using, for example, commercialmixers designed for powder handling. In general, the blending can beperformed in a batch or more continuous type processing. For batchmixing, appropriate amounts of each powder are placing into a mixingvessel, which can have mixing blades or the like. For more continuousblending, an auger or screw conveyor or the like can be used with a feedinto the device to provide the desired polymer ratios. Following mixingof the powders to form a homogeneous blend, the powders can be bagged orplaced in another suitable container for distribution. In alternativeembodiments, the powder blends are formed on site in which the mixing isperformed shortly prior to use. In any case, blended powders can beplaced in a suitable hopper for metered delivery.

The addition of polyethylene oxide can result in larger flocs andtherefore the ability to reduce the amount of polyDadmac used to createa clear supernatant. PEO dissolves quickly, especially for the fine PEOparticles, allowing for a rapid flocculation properties with acorresponding reduction of surface area of suspended particulates in theflow. Residual suspended turbidity, such as suspended anionic material,can be attracted to and agglomerated by the positively charged Dadmac toproduce a clearer supernatant with a reduced amount of polyDadmac.

To achieve the desired purpose of the suspension embodiments, thesuspensions do not need to be stable and as a general matter may not be,although it is not problematic if the suspensions are coincidentallystable. Stability in this context is intended to mean that a well mixedsuspension remains homogenous. In general, the suspensions separate withthe solids concentrating toward the bottom of a container due togravity. However, the suspensions can be mixed to form a homogenoussuspension when desired, such as for delivery for a particularapplication, as described further below.

In contrast to the suspension described herein, stable suspensions ofPEO have been described in U.S. Pat. No. 3,843,589 to Wartman (Wartman'589 patent), entitled “Stable Pumpable Slurries of Ethylene OxidePolymers,” incorporated herein by reference. To achieve the stablesuspension, the Wartman '589 patent described a more complex liquid toachieve a suitable density, certain specific polymer parameters, a veryhigh viscosity suspension In contrast, the present suspensions may notbe stable, but they have significantly lower viscosities for easierdelivery and simpler formulations. The liquids used for the suspensionsgenerally have a viscosity at 25° C. in some embodiments of no more thanabout 400 centipoise (cP), in other embodiments no more than about 300cP and in further embodiments no more than about 250 cP. The wellblended suspension can have a viscosity at 25° C. of no more than about1000 cP, further embodiments no more than about 850 cP and in additionalembodiments no more than about 750 cP.

For use, the suspended flocculant polymers can be diluted with waterprior to delivery into the waste stream or other delivery stream. Thepolyether polyol generally mixes with water and the flocculant polymergenerally dissolves. During the dissolving/make down step, the liquidstate of the polymer suspension improves initial distribution of polymerparticles compared to an equivalent dry fed product that may experienceclumping during the wetting phase. Testing has shown that PEO particlesdelivered with the suspension into water results in rapid dissolving ofthe PEO, and it is expected that the other polymer should exhibitsimilar rapid dissolving. The suspension can be delivered from asuitable mixer to provide for delivery of a uniform composition,generally in selected metered amounts, and delivered into a containerfor dilution with water. The flocculant polymer compositions isgenerally formed into a dilute aqueous solution generally at aconcentration from about 0.0005 to about 0.2 weight percent, in furtherembodiments from about 0.001 to about 0.1 weight percent and inadditional embodiments from about 0.002 to about 0.05 weight percentflocculant polymer(s). A person of ordinary skill in the art willrecognize that additional ranges within the explicit ranges above arecontemplated and are within the present disclosure.

Flocculants are useful for the treatment generally of waste streams,generally from mines, to agglomerate particulates that can then settlefrom the waste stream and to facilitate concentration of theparticulates. Mines generally produce flow of relatively dilute wastestream with tailings, also referred to as mineral slimes. To reasonablydispose of the mineral slimes, the concentration of particulates can beconcentrated. The polymer flocculants described herein can be effectiveto form flocculants, for example, with clay, claylike waste or othersilicate or metal oxide particulate waste, which can be produced invarious mining operations, such as phosphate mining, bauxite mining,coal washing, dredging, talc mining, other sand mining deposits, aluminaprocessing and the like. The dissolved polymer flocculants can beinjected into the stream containing suspended solids that is thendirected to a settling tank, or the like. Processing with the polymerflocculants is described further below.

With the use of a polyacrylamide flocculant and/or a polyDadmacflocculant, the flocculant is generally added in part early in the wasteflow with optional additional portions added along the flow to drive arelatively slow flocculation process to a relatively effective endpoint. With the use of polyethylene oxide alone, it is generallydesirable to add the flocculant essentially at or near the point ofentry of the waste flow into a settling tank due to the relatively rapidflocculation effect. With respect to the polymer blends, the flocculantcan be added upstream in the waste flow from the entry point into thesettling tank or center well. Proper mixing of a polymer blendfacilitates this earlier delivery without interfering with the desirableflow of the waste stream through conduits leading to a settling tank. Ifthe polymers are delivered in a water dilution flow, the degree ofdissolving can be controlled to yield a desired state of the materialwhen delivered into the waste stream, fiber de-watering site or othersite for use. An earlier delivery of flocculant provides for improvedmixing within the waste flow, which can result in the reduced use offlocculant while improving the effectiveness of the flocculant. Inparticular, in some embodiments a polymer flocculant is added at least10 meters upstream from a port, e.g., central inlet, into a settlingtank.

Flocculant polymer particle suspensions or powder polymer blends can beadded directly to a waste stream, or can be added by using a water flowdelivery to pre-dilute the flocculant polymer component prior toentering the waste stream. The use of a water dilution flow allows forone or more of the flocculant polymers to be dissolved to a desireddegree prior to entering the waste stream. Any reasonable water sourcecan be used to generate the water dilution flow. When a water dilutionflow delivery is used, a selected flow of water with an amount of thepolymer powder blend is directed into the waste stream. To control thedegree of solubilization of the polymer particles especially thepolyDadmac, the powder blend or suspension is added to this dilutionflow to create an initial aqueous combination. The selected rate of flowcan be based on the solubility of the flocculants, the desireddissolution of the flocculants prior to entering the waste stream andthe physical configuration of the components. In some embodiments, thepowder blend, for example, can be diluted no more than about 5 minutesprior to entering the treatment stream, in further embodiments no morethan about 2 minutes, in other embodiments no more than 60 seconds, infurther embodiments no more than 30 seconds, in further embodiments fromabout 1 to about 20 seconds, and in further embodiments from about 5 toabout 15 seconds prior to entering the treatment stream, fiberdewatering site, or other use location. A representative configurationfor a water dilution flow within a treatment system is shown below. Theuse of a water dilution flow allows for flocculant polymer particles todissolve prior to entering the waste stream, while polyDadmac particlesmay only dissolve significantly after entering the waste stream. Aperson of ordinary skill in the art will recognize that additionalranges within the explicit time ranges above are contemplated and arewithin the present disclosure.

A representative configuration of a waste treatment facility for thetreatment of waste water with mining tailings is shown in FIG. 1. Thewaste treatment facility for a mining operation comprises mineralprocessing stations 102, 104, 106, slime flow conduit system 108,thickening tank 110 and polymer flocculant delivery system 112, which inparticular is suitable for polymer suspension delivery. Theconfiguration of the mineral processing stations can depend on theparticular mining operation, and these stations can comprisehydrocyclones 120 or the like or other suitable purification equipmentto separate crudely purified mineral ore from slimes, i.e., dilutetailing waste from the mineral separation. In some embodiments, amineral processing station can comprise a head box 122, 124, 126 todirect slime/waste flow from a mineral processing station to the wasteflow conduit system. While FIG. 1 shows three mineral processingstations 102, 104, 106, in other embodiments a waste facility mayinterface with a single mineral processing station, two, four, five ormore than five mineral processing stations.

Slime flow conduit system 108 provides for flow of the waste stream frommineral processing stations 102, 104, 106 to thickening tank 110, andgenerally slime flow conduit system 108 interfaces with polymerflocculant delivery system 112 at one or more points. With theconfiguration shown in FIG. 1, slime flow conduit system 108 comprisesflow lines 130, 132, 134 that lead to combined flow line 136. Flow lines130, 132, 134, respectively connect to head boxes 122, 124, 126 toreceive slimes from mineral processing stations 102, 104, 106,respectively. The size and construction of flow lines 130, 132, 134, 136can be designed based on the particular mining operation andcorresponding waste volumes, and flow limes 130, 132, 134, 136 can bepipes, open or closed ducts or any other suitable flow structure. For arepresentative phosphate mining operation flow lines 130, 132, 134 canbe pipes with a diameter of roughly 10-40 inches, and combined flow line136 can be a pipe with a diameter of roughly 30-60 inches, but the basicteachings herein can apply to a range of processing operations andmining volumes. As noted above, a particular system can comprise adifferent number of mineral processing stations and correspondingmodifications to slime flow conduit system 108 follow from the teachingsherein.

Thickening tank 110 can comprise a tank structure 140, a central inlet142, a clarified water outflow 144 and a tailings outflow 146. Tankstructure 140 can have a suitable volume for the particular miningoperation size. Central inlet 142 provides an interface with combinedflow conduit 136 such that slime can enter the tank structure 140.Central inlet 142 can be simply an end opening of combined flow conduit136, but in some embodiments, central inlet 142 can comprise a circularring like structure with optional mechanical mixing to provide for amixed slime flow into tank structure 140 to facilitate flocculation. Inthe thickening process that takes place in tank structure 140, theflocculates solids have a higher density and fall to the bottom of thetank, and less dense clarified water can be found near the top of thetank. Clarified water outflow 144 can be configured to take off waterfrom near the top of the tank, such as the top 20%-40% of the tankvolume and in further embodiments the top 10% of the tank volume, and ingeneral near the edge of the tank. Similarly, tailings outflow 146 canbe configured to withdraw concentrated tailings from the flocculationprocess near the bottom of the tank and in some embodiments toward thecenter of the tank, in some embodiments from the bottom 20% of the tankvolume and in further embodiments from the bottom 10% of the tankvolume. A person of ordinary skill in the art will recognize thatadditional ranges of positions for water removal within the explicitranges above are contemplated and are within the present disclosure.

Referring to FIG. 1, polymer flocculant delivery system 112 comprises apolymer suspension reservoir 150 that can comprise a mixer to maintain arelatively homogenous form of the suspension, a mixing/dilution tank152, a storage tank 154 and feed lines 156. Polymer suspension reservoir150 generally holds a desired quantity of the selected polymer blend andcan comprise a feed valve 158 or the like to provide for the placementof a selected amount of polymer into mixing/dilution tank. Polymersuspension reservoir generally can provide continuous mixing of thepolymer suspension so that a homogenous polymer suspension can be meterout of the reservoir. Mixing/dilution tank 152 generally has anappropriate mixing element and can be configured generally to operate ina batch or continuous mode of operation. Water is generallycorrespondingly delivered into mixing/dilution tank 152 to provide adesired concentration of polymer solution, as described above. The mixedpolymer solution can be pumped or otherwise flowed for storage tostorage tank 154 for delivery as needed to the waste stream through feedlines 156. In alternative embodiments generally for the delivery of asuspension comprising polyDadmac, polymer suspension reservoir 150 canbe configured for direct delivery of polymer suspension into feed lines156 or a portion thereof. Referring to FIG. 1, a mixing flocculantreservoir 157 is configured for direct delivery of a flocculantsuspension through line 159 to head box 124, which can be, for example,desirable for the delivery of a suspension of polyDadmac or copolymersthereof.

As noted above, it can be desirable to directly deliver the polymerparticle suspensions with dilution water without storage in a reservoirwith an aqueous solution. The use of direct delivery with a dilutionwater flow provides for more controlled dissolving of the polymerparticles. Referring to FIG. 2, direct polymer flocculant deliverysystem 161 comprises a polymer suspension reservoir 163 that cancomprise a mixer to maintain a relatively homogenous form of thesuspension, a water supply line 165, and feed line 167. Polymersuspension reservoir 163 generally holds a desired quantity of theselected polymer blend and can comprise a feed valve 169 or the like toprovide for the placement of a selected amount of polymer into the watersupply line 165 at a predetermined rate. Polymer suspension reservoir163 generally can provide continuous mixing of the polymer suspension sothat a homogenous polymer suspension can be metered out of thereservoir. The water supply line 165 generally has a controlled flowrate selected to allow for proper dissolution of the polymers prior toentering the waste stream as described above. The length of time thepolymer is in the water flow can be determined by the length of thepipe, the diameter of the pipe, the flow rate or a combination thereof.The arrows indicate the direction of the flow. In some embodiments, thediameter of the water supply pipe 165 can be about 0.1 inch to about 1inch, although particular application generally suggest desired flowvolumes. Feed line 167 can connect, for example, with the feed line 156or with feed line 159 or other alternative configurations to havedesired flow lengths and flow volumes based on selected delivery pointsfor the delivery of a suspension of polyDadmac, copolymers thereof, PEO,polyacrylamides and/or selected blends thereof.

Feed lines 156 provide for flow from storage tank 154 to slime flowconduit system 108, and pumps can be used as appropriate to drive theflow. As shown in FIG. 1, feed lines 156 comprise 5 branch feeds 160,162, 164, 166, 171 from main feed line 168, which connects with storagetank 154. The feed lines can be appropriate pipes or other conduits.Branch feeds 160, 162, 164, 166, 171 connect between main feed line 168and delivery connections 180, 182, 184, 186, 188 that connect withcorresponding points of the slime flow conduit system. As shown in FIG.1, delivery connection 180 is located at head box 124, deliveryconnection 182 is on flow conduit 132, delivery connections 184, 186 arelocated at different points on combined flow conduit 136, and deliveryconnection 188 is located at central inlet 142. In additional oralternative embodiments, a different number of branch flow conduits canbe used, such as 1, 2, 3, 4, 6 or more than 6, and the positions of thedelivery connections can be altered as desired. Similarly, a system cancomprise more than 1 polymer flocculant delivery system if desired tosupply polymer solution to various delivery connections.

As noted above, based on the improved polymer blends described hereinthe solution of the polymer blend can be effectively added at selectedlocations along the slime flow. While polyethylene oxide alone as aflocculant has desirable properties, the flocculant action of thepolyethylene oxide is most effective when the flocculant solution isadded essentially at the central inlet into the thickening tank, e.g.,delivery connection 188 in FIG. 1. The delivery of a polymer flocculantsolution at or near the central inlet limits the mixing with the wastestream prior to entry into the thickening tank. It has been discoveredthat some flocculant polymer blends described herein provide for earlierintroduction into the waste flow to provide better mixing with the wasteflow. Overall the polymer blends provide outstanding flocculant functionand improved delivery flexibility. In contrast with high molecularweight polyethylene oxide alone, flocculant polymer blends can bedelivered effectively through a delivery port into the slime flow atleast 10 meters from the port connecting the waste flow with thethickening tank settling zone, in further embodiments at least about 12meters and in additional embodiments from 15 meters to the initiation ofthe waste flow adjacent to the mineral processing station. A person ofordinary skill in the art will recognize that additional ranges ofdistances within the explicit ranges above are contemplated and arewithin the present disclosure.

For the delivery of powder particle blends, polymer flocculant deliverysystem 112 or portions thereof can be replaced with appropriatecomponents for the delivery of the polymer blend. For example, areservoir of powder can be directly connected at delivery connections180, 182, 184, 186, 188. The powder blends can then be directlydelivered at selected rates into the flow. As noted above, in someembodiments, a dilution water flow can be used to deliver the polymerblend with some dissolving of the flocculant polymer. A dilutedflocculant blend delivery system can be directed individually to one ormore delivery connections and/or to branched feeds directed to two ormore delivery connections.

FIG. 3 shows a system configured for the delivery of a flocculant power,e.g. a flocculant powder blend, into a dilution water flow for deliveryto a waste processing system. Referring to FIG. 3, polymer powderdelivery system 210 comprises a powder polymer blend hopper 212, a watersupply line 214, and a feed line 216. Powder polymer blend hopper 212generally holds a desired quantity of the selected polymer blend and cancomprise a valve with a gravity feed, helical auger 218 or othermechanical feed, or the like to provide for the placement of a selectedamount of powder polymer blend into the water supply line 214 at apredetermined rate. The water supply line 214 generally has a controlledflow rate selected to allow for desired dissolution of the polymersprior to entering the waste stream as described above. The length oftime the polymer is in the water flow can be influenced by the length ofthe pipe, the diameter of the pipe, the flow rate, or a combinationthereof. In some embodiments, the diameter of the water supply pipe 214can be from about 0.1 inch to about 1 inch, although the pipe parametersmay be significantly influenced by the particular application. Arrowsindicate the direction of the flow. Water supply line 214 can connectwith the feed lines 156, feed line 159 or other desired configuration toconnecting to selected delivery connections 180, 182, 184, 186, 188 witha selected length of pipe for the delivery of a selected flocculantpowdered polymer or blends thereof.

While the polymer flocculants can be effectively used in various wasteprocessing situations and/or fiber dewatering processes, it isinstructive to review a representative procedure. For example, a slimeflow coming from the mineral processing stations can have a solidsconcentration from about 1 weight percent to about 12 weight percent.The objective can be to concentrate to solids in the waste to levelsgenerally from about 15 to about 45 weight percent and in furtherembodiments from about 20 to about 35 weight percent in the under flowremoved from the thickening tank. The clarified water removed from thethickening tank can have at least about 90 percent, in some embodimentsat least about 95 percent, and in further embodiments at least about 99of the initial solids removed. In general, the volume of polymerflocculant solution is added in a dosage from about 1 parts per millionby weight (ppm) to about 50 ppm, in some embodiments from about 5 ppm toabout 40 ppm, and in further embodiments from about 10 ppm to about 30ppm of polymer flocculant within the treated slime flow, i.e., 1 partpolymer per million parts of waste water by weight assuming that thewaste water is 1 kg per liter. A person of ordinary skill in the artwill recognize that additional ranges of processing parameters withinthe explicit ranges above are contemplated and are within the presentdisclosure. The improved polymer blends and/or the improved delivery ofthe polymer blends provide for a reduced use of polymer in order toachieve a desired high purity of water effluent.

In addition to cleaning mining sewage, the flocculant polymers can beeffectively used in other waste water treatment context, such as toremove fibrous particulates from waste streams. Thus, flocculantpolymers can be effectively used for waste water treatment from papermills and the like. Paper mill dewatering processes can be performed toform fiber cakes that can be recycled into useful materials. Thickeningof fiber sludge can be performed by filtration or sedimentation, such aswith clarifiers or floatation units. To facilitate cake formation, thedewatering process can involve screw presses, belt presses, centrifugesor other dewatering of waste fibers. A fiber cake can have a solidcontent of at least about 20 weight percent and in some embodiments atleast about 25 weight percent. The initial sludge can have a solidcontent generally from roughly 1 weight percent to about 15 weightpercent. The use of flocculant polymers generally for the treatment ofwaste streams from paper mills, pulp mills or deinking plants isdescribed generally in U.S. Pat. No. 6,123,856 to Kumpera et al.,entitled “Dewatering of Sludges,” incorporated herein by reference.

Furthermore, flocculant polymers can be useful as fiber retention agentsin paper making processes and the like for fiber materials. Paper isformed on a screen or the like where the fibrous material is dewateredto form the paper. The retention of fibers in the paper both increasesyield of the paper product and reduces fiber particulates in the millwaste stream, which can increase the clean up burden. Thus, smallquantities of the flocculant polymers can be combined with the paperforming material to reduce fiber loss from the material duringdewatering. The use of cationic or anionic polyacrylamide polymers toaid in paper dewatering is described in U.S. Pat. No. 4,795,531 to Sofiaet al., entitled “Method for Dewatering Paper,” incorporated herein byreference. To improve the dewatering aid, a portion of high molecularweight PEO can be combined with the polyacrylamide to form a flocculantpolymer blend. The blend can comprise from about 1 weight percent toabout 40 weight percent PEO, in other embodiments from about 5 weightpercent to about 38 weight percent PEO and in further embodiments fromabout 10 weight percent to about 35 weight percent PEO, and in someembodiments the remainder of the flocculant polymer can be cationicpolyacrylamide. A person of ordinary skill in the art will recognizethat additional ranges of PEO polymer in a blend of flocculant polymerswithin the ranges above are contemplated and are within the presentdisclosure.

Suspended samples of high molecular weight PEO polymers alone or mixedwith polyacrylamide (PAM, 30% anionic) were prepared with PEG 400suspending liquid. Several different brands of high molecular PEO weretested with similar results. The samples are mixed in a jar and allowedto settle. When mixed the suspensions produced a liquid that was uniformto visual inspection. The polymer particles gradually settled toward thelower portion of the jar. FIG. 4 shows seven samples following settling,which was observed to generally take place over roughly 5-7 hours. Thecomposition of these samples in weight percent is as follows from leftto right.

1. 70% PEG 400, 15% PEO, 15% PAM

2. 82% PEG 400, 18% PEO

3. 80% PEG 400, 20% PEO

4. 70% PEG 400, 30% PEO

5. 80% PEG 400, 10% PEO, 10% PAM

6. 80% PEG 400, 10% PEO, 10% PAM

7. 80% PEG 400, 20% PEO

After settling, the polymers could be easily re-suspended into avisually homogenous liquid through simple swirling of the jars. Afterre-suspension, the polymer would then settle again over the course ofseveral hours.

The embodiments above are intended to be illustrative and not limiting.Additional embodiments are within the claims. In addition, although thepresent invention has been described with reference to particularembodiments, those skilled in the art will recognize that changes can bemade in form and detail without departing from the spirit and scope ofthe invention. Any incorporation by reference of documents above islimited such that no subject matter is incorporated that is contrary tothe explicit disclosure herein.

What is claimed is:
 1. A composition comprising a blend of a particulatepolyethylene oxide having an average molecular weight from about1,000,000 g/mol to about 15,000,000 g/mol and a particulatepolyacrylamide, the particulate polyacrylamide being anionic ornon-ionic, wherein the particulate polyethylene oxide has at least about10 weight percent of particles having a particle diameter of no morethan about 75 microns.
 2. The composition of claim 1 wherein theparticulate polyethylene oxide has an average molecular weight fromabout 3,000,000 g/mol to about 10,000,000 g/mol and wherein theparticulate polyacrylamide has an average molecular weight of at leastabout 22.5 million g/mol.
 3. The composition of claim 1 wherein theparticulate polyethylene oxide has at least about 60 weight percent ofthe particles having a particle diameter of no more than about 75microns.
 4. The composition of claim 1 wherein the particulatepolyethylene oxide has at least about 10 weight percent of the particleshaving a particle diameter of no more than about 50 microns.
 5. Thecomposition of claim 1 wherein the particulate polyacrylamide has anaverage molecular weight of at least about 16 million g/mol.
 6. Thecomposition of claim 1 wherein the blend is homogeneous.
 7. Thecomposition of claim 1 wherein the blend has a concentration ofparticulate polyethylene oxide from about 45 weight percent to about 90weight percent.